Water quality interventions
Summary – Water quality interventions (e.g., filtration, chlorination) aim to prevent waterborne disease, particularly diarrheal disease, a major cause of death among children in developing countries, by removing or disabling pathogens in water.
There is little debate that contaminated water causes diarrhea and that the methods used in interventions to improve water quality, chlorination for example, reduce contamination. However, in developing world settings where diarrhea is endemic, because of a lack of sanitation, hygiene, and access to safe water, the evidence for the effectiveness of these interventions is less clear.
Many randomized controlled trials in the developing world find that water quality interventions reduce diarrheal disease. But these trials are unblinded and rely on self-reported diarrhea to evaluate the interventions. None of the small number of blinded trials of water quality interventions has shown an effect. These blinded trials, like some of the unblinded studies, have various methodological weaknesses, and these weaknesses may undermine their conclusion.
Overall, we are ambivalent about the effect of water quality interventions on diarrhea. We find plausible theories grounded in the available evidence for both believing that water quality interventions reduce diarrhea and for the more pessimistic conclusion that these interventions do not have an effect. We also do not see any analysis that may lead to a more definitive answer without a significant, additional investment of time. We therefore summarize our work so far, provide feedback we’ve received from scholars and leave questions for further investigation.